This invention relates to a cage for a roller bearing, a method for manufacturing the same, and a roller bearing having such a cage mounted therein, and more particularly to an improved cage which can prevent fretting and abnormal noise while in operation.
A roller bearing is used as an idler bearing for a car transmission. When shifting the gear positions in the transmission, the gears are rotated under load together with the shaft, so that in the roller bearing, the relative rotation speed between the raceway members and the rollers becomes zero. Namely, in this state, the relative position between the raceway members and the rollers is maintained. Thus, at frequently used shift positions, the raceway members and the rollers tend to suffer fretting on their surfaces due to vibrations while the car is moving.
One way to prevent such fretting is to form roller receiving pockets in the cage at unequal pitches. By forming the pockets at unequal pitches, the rollers are prevented from stopping at the same positions. This makes it possible to delay the onset of fretting. But since the cage has an integral one-piece structure, if the shaft and the housing are rotated in unison for a long time, e.g. if the car is driven with the same shift position for a long time, no relative rotation will occur in the bearing, so that fretting is not completely eliminated.
Further, in order to form pockets at unequal pitches, the entire cage has to be formed solely by cutting. This results in lower productivity and thus higher production cost.
Another way to prevent fretting is the use of a split cage formed with a cut. By splitting the cage, it can rotate relative to the other parts of the bearing, so that fretting can be prevented effectively.
In this type of cage, there are single-cut cages and double-cut ones. The former is usually limited to ones made of synthetic resin. Thus, such a cage cannot be used at too high temperatures. If such a single-cut cage is formed of metal, such restrictions in the use conditions are eliminated. But when a ring-shaped metal member is cut at one point after forming pockets to obtain a single-cut cage, residual stresses in the metal cage are released, so that the cut portion tends to open up remarkably.
A double-cut cage is a cage cut apart into two separate parts. These two separate parts have to be mounted individually between the inner and outer raceway members. Thus, assembling such a cage into a bearing is very difficult and troublesome.
An object of this invention is to provide a cage for roller bearing which can prevent fretting and abnormal noise during operation of the bearing, and which can be easily manufactured and assembled into a bearing.
Another object of this invention is to provide a method for manufacturing such a cage with high accuracy and at low cost.